1. Field of the Invention
The invention generally relates to valves for pressurized tanks or other pressurized containers, e.g., pressurized gas bottles. More particularly, the invention relates to valves for pressurized containers which are commercially characterized as being “non-refillable” or “no-return” containers and which, for reasons of safety and otherwise, are not intended for re-use after their initial contents have been emptied. Valves for such containers are also often referred to in the art as “single use” valves for pressurized containers.
2. Description of the Related Art
Pressure tanks or other pressure containers are usually filled under carefully controlled conditions at a charging station and then distributed to other places for use. When empty it is intended that the containers be returned to the charging center for appropriate reuse or destruction in the case of single use containers. Unfortunately, the attractive economies of refilling containers at points of use or otherwise repressurizing them under less than carefully supervised conditions has resulted in the introduction of impurities or inferior refills and, more seriously, in injurious explosions. The reuse of pressure containers is highly objectionable for many reasons which relate to safety.
So-called “non-refillable valves” are well known in the prior art. Specific examples of known valves include valves of the type described in U.S. Pat. No. 4,543,980, to van der Sanden, issued Oct. 1, 1985; valves of the type described in U.S. Pat. No. 4,573,611, to O'Connor, issued Mar. 4, 1986, and the various prior art valves described in the aforementioned patents. Both the van der Sanden and O'Connor patents mentioned above are incorporated herein by reference.
In the van der Sanden patent, reference is made to techniques in which one-way ball valves can be used in conjunction with pressurized containers so as to allow for them to be initially charged through an orifice, and wherein further charging is prevented once the initial charge has been completed. The prevention of further charging is performed by forcing a ball past a constriction into a final location in a manner such that it cannot return above the restriction. Once the ball is in this final location, it will block any further refilling by simply seating in the q1valve. However, as noted by van der Sanden, the use of a ball valve is somewhat intricate and complex and requires careful precision machining.
Walker in U.S. Pat. No. 3,985,332 discloses a non-refillable safety valve for a pressurized container. The valve includes a housing having a central bore, a hollow knob unit also having a central bore, and a core having a central bore which is slideably mounted in the central bore of the housing. The hollow knob unit is in threaded engagement with the outer wall of the housing. The central bore of the housing provides communication between a port and the pressurized container for charging and selectively discharging of the pressurized container. A sealing member is provided which is slideably mounted in the lower end portion of the central bore of the core. An outwardly biased spring snaps outwardly into a channel to prevent the knob unit from being completely unscrewed. An element prevents the pressurized vessel from being refilled. This device was characterized by van der Sanden as being complex and expensive to manufacture.
Van der Sanden describes a valve for a pressurized container having a blocking element therein which is adapted to occupy an initial location in which fluid can move in and out of the container past the blocking element. According to van der Sanden, the valve and blocking element are further configured such that the blocking element can be irreversibly moved to a position in which the valve permits the escape of fluid under pressure exerted from inside the container, but which automatically closes in response to exposure to an external pressure greater than the pressure inside the container. The blocking element is formed of at least one radially extending arm whose lateral radius is reduced upon movement of the blocking element from the initial location to the final location. Then, at least one arm expands within the final location to prevent return of the blocking element to the initial location.
The non-refillable valve taught by van der Sanden, although offering manufacturing advantages over the prior art valve designs known at that time, still requires the use of a complex and relatively costly manufacturing process and, also, suffers from certain performance limitations as well.
In particular, the valve housing described by van der Sanden requires the formation of manufactured undercuts or “blinds” in order to function properly. For example, the undercut shown at reference number 37 in van der Sanden FIG. 1 (where the central core of the valve shown in FIG. 1 is wider immediately below location 37 than it is immediately above that location) is a requirement for practicing the referenced invention and adds complexity and expense to the valve housing manufacturing process. Furthermore, the blocking element is “directional”, that is, it needs to be carefully inserted in the proper direction during the manufacturing process for the valve to work at all.
In addition, in the valve taught by van der Sanden, the blocking element is held in its initial position (to facilitate initial charging of the container) by a connection of the blocking element to a stem, rod or some other valve component, or the operation of the blocking element is dependent on the proper operation of another movable internal valve component, such as a slideable rod, etc., for its proper positioning. Steps such as these can complicate the valve manufacturing process. Operationally, this requirement can introduces a potential performance limitation affecting valve reliability because blocking element linkage with or dependency on other valve components becomes a factor in achieving valve reliability.
The O'Connor non-refillable valve differs in many respects from the teachings of van der Sanden. For example, the O'Connor valve uses pressure instead of a mechanical force to release the primary valve seal; O'Connor utilizes the same element for making a primary valve seal when closing the valve as is used (i.e., the element doubles as) the blocking element, etc. However, many of the same problems inherent in manufacturing a non-refillable valve are common to both van der Sanden's teachings and those of O'Connor such as, for example, the requirement that the valve housing used have manufactured undercuts, the blocking element used is still “directional”, i.e., it needs to be carefully inserted in the proper direction during the manufacturing process for the valve to work.
Non-refillable valves desirably fill the following requirements: (a) the need for a dual purpose manufacturing process that uses a single basic valve design to enable both refillable and non-refillable valves to be manufactured using essentially the same parts list, machine tools, etc.; instead of the present practice of having to execute dedicated manufacturing process for producing refillable versus non-refillable type valves (because of differing housing types that are used, different components required for valve operation, etc.); (b) the need for a valve design (both refillable and non-refillable) that utilizes a mechanically operated primary sealing mechanism (as opposed to valve designs that utilize a pressure differential to open the primary sealing mechanism) to insure seal quality while solving the other problems with known valves indicated hereinabove; (c) the need for a valve design that prevents rotation of the primary sealing mechanism in the valve housing to minimize wear, extend valve life and further improve seal quality; (d) the need for a valve design in which the primary sealing mechanism and means for controlling the opening and closing of the valve are optionally made from discrete components formed from different materials to enable the sealing mechanism to be chemically compatible with the fluid contents of the container even when the controlling mechanism (means for controlling the opening and closing of the valve) is not; and (e) the need for a valve design, solving all of the aforementioned problems and meeting the aforestated needs, which is relatively simple and inexpensive, which will allow normal filling of the pressure container under proper conditions, adequate sealing of the pressure during nonuse, selective discharge of the pressure container and, in the case of the non-refillable valves contemplated by the invention, provide effective protection and prevention against improper and unauthorized filling of the container.
Mohn, U.S. Pat. No. 5,794,660 describes a non-refillable valve for a pressurized container which includes a unidirectional stepped valve housing within which a freestanding blocking element is housed. The blocking element is preferably a reversible, symmetrical check that integrally includes stop means for preventing the return of said blocking element to an initial location after it has been moved to a final location that activates the one way characteristic feature of a non-refillable valve (where activation is designed to take place after initially charging of the container).
De Fu Chen, U.S. Pat. No. 6,595,486 describes a non-refillable valve assembly that includes a valve stem and valve seat that is slidably received in the valve stem. Initially, the valve seat resides in a first position above a rim or protrusion in the valve body. After filling the valve seat is pushed past the rim or protrusion by operation of the valve stem, thus sealing the container and also preventing refilling.
Thus, it can be appreciated that it remains desirable to have new valve designs that provide the needs discussed hereinabove and yet remain relatively simple and inexpensive to produce.